This invention generally relates to an improved lock rod clamping apparatus for detachably connecting a tool unit to a tool supporter, and is particularly concerned with such an apparatus having an increased gripping force.
Clamping mechanisms for detachably connecting a tool unit to a tool supporter are well known in the art. One typical use of such mechanisms is in machining operations where the tool unit holds a cutting insert that is moved into and out of cutting engagement with a rotating metal workpiece. The clamping apparatus allows different tool units holding different cutting inserts to be quickly attached to and detached from the tool supporter which in turn is connected to a device that controls the movement of the tool units with respect to the workpiece.
One of the most commercially successful clamping mechanism includes a cylindrically-shaped canister member that is matable with the tubular end of a tool unit and which includes apertures for admitting locking elements into locking engagement with recesses present in the tool unit. The locking elements, which are typically spherical, are radially moved through the apertures in the canister member by means of cam surfaces present on a reciprocating lock rod. Examples of such a clamping mechanism are disclosed in Erickson U.S. Pat. Nos. 4,708,040; 4,747,735; 4,836,068, and 4,932,295, each of which is assigned to Kennametal Inc. located in Latrobe, Pa.
Such a prior art clamping mechanism is illustrated in FIG. 4. Here, a side, cross-sectional view of the distal end 62 of a canister member 39 is shown which includes an aperture 54a in the form of a cylindrical bore through the wall of the member 39. The inner diameter of the circular bore forming the aperture 54a closely approximates the outer diameter of the spherical locking element 57a. A reciprocating lock rod 60 includes a cam portion 64a having a spherical depression 66 which tapers off into a ramp 68. When the spherical locking element 57a is seated in the depression 66, and the lock rod 60 is moved against the bias of the springs 74 (shown in FIG. 3) toward the distal end of the canister member 39 so that its stop flange 70 is in the position illustrated in FIG. 3, the spherical element 57a is in a non-locking position. This unlocking position allows the tubular shank 16 of a tool unit 10 to be inserted into the annular recess 59. However, when the springs 74 are released to pull the lock rod 60 away from this position toward the position illustrated in FIG. 4, the ramp of the cam portion 64a wedgingly engages and radially raises the spherical locking element 57a into the locking position shown. In such a position, the spherical locking element will wedgingly and lockingly bear against the angled wall 30 of the tool unit 10.
While such a prior art locking mechanism has proven its capability of quickly, conveniently, and rigidly attaching a tool unit to a tool supporter, the applicant has observed an area where the performance of such a mechanism could be substantially improved. Specifically, the applicant has observed that if the clamping mechanism could be modified to increase the clamping force applied to the tool unit without increasing the pull-back force that the spring package applies to the lock rod, then a smaller and shorter spring package could be used to achieve the same holding force. Such a smaller spring package would advantageously shorten the envelope of the tool, which in turn would render the tooling system incorporating the clamping mechanism easier and more convenient to use in a working environment. Additionally, the life span of the springs used in the package (which are typically Bellville washers) would be lengthened. Alternatively, if a spring package of conventional size were used, the holding force between the clamping mechanism and the tool unit would be increased, which in turn would increase tool rigidity and enhance the accuracy of the cutting operation.
Clearly, it would be highly advantageous if a way could be found to increase the holding force that such a clamping mechanism generates with respect to a tool unit for a given pull-back force on the lock rod to make possible either the use of a small spring package, with a consequent reduction in the overall size of the tool envelope or an increase in tool rigidity and cutting accuracy with the use of a spring package of conventional size. Ideally, such a holding force-increasing solution should require only a minimal amount modification to the shapes of existing parts so that a conventional clamping mechanism of the type previously described could easily be converted into an improved clamping mechanism with a minimum amount of disassembly and machining.